this hook allows the registration of Custom Taxonomies in Subscribe2 so that notifications assigned to such custom taxonomies can still generate an email notification.this hook allows the registration of Custom Taxonomies in Subscribe2 so that notifications assigned to such custom taxonomies can still generate an email notification.

function my_taxonomy_types($taxonomies) {
    $taxonomies[] = 'my_taxonomy_type';
    return $taxonomies;
}
add_filter('s2_taxonomies', 'my_taxonomy_types');